The Spatial Module for Apache Lucene

The spatial module is new to Lucene 4, replacing the old "contrib" module
that came before it. The principle interface to the module is
a SpatialStrategy
which encapsulates an approach to indexing and searching
based on shapes. Different Strategies have different features and
performance profiles, which are documented at each Strategy implementation
class level.

For some sample code showing how to use the API, see
SpatialExample.java in the tests.

The spatial module uses
Spatial4j
heavily. Spatial4j is an ASL licensed library with these capabilities:

Provides shape implementations, namely point, rectangle,
and circle. Both geospatial contexts and plain 2D Euclidean/Cartesian contexts
are supported.
With an additional dependency, it adds polygon and other geometry shape
support via integration with
JTS Topology Suite.
This includes dateline wrap support.

Historical note: The new spatial module was once known as
Lucene Spatial Playground (LSP) as an external project. In ~March 2012, LSP
split into this new module as part of Lucene and Spatial4j externally. A
large chunk of the LSP implementation originated as SOLR-2155 which uses
trie/prefix-tree algorithms with a geohash encoding. That approach is
implemented in RecursivePrefixTreeStrategy
today.